This invention relates to a propulsion cage which can be separated into segments and which is in shape-mating relationship to a subcaliber projectile; the cage exhibiting a forward guide zone and a propulsion zone with a driving surface, the profile of the driving surface approaching the peripheral area of the subcaliber projectile with constant tapering, starting with the guide zone.
In order to fire a subcaliber projectile, a propulsion cage is utilized, the cage transmitting essentially the pressure of the propellant gases to the subcaliber projectile for acceleration and serving as a guide for the subcaliber projectile within the barrel of a weapon. The propulsion cage for a subcaliber projectile is a rotationally symmetrical member subdivided into (usually three) segments by separating cuts so that the cage disintegrates after leaving the barrel of the weapon and drops off the subcaliber projectile.
A conventional propulsion cage (De 3,033,041-A) exhibits a guide zone, for example in the form of a forward guide plate, and a propulsion zone, in most cases also in the form of a rearward driving plate, and thus approximates the shape of a dog's bone, i.e. a bone with joints on proturbances at each end.
The kinetic energy which can thus be transmitted to a subcaliber projectile is limited due to the properties of the material of the subcaliber projectile. The stresses that occur must be influenced by the structure of the cage and an energy transmission is possible which is the higher, the lower the maximum compressive strains and tensile stresses caused by the propellant gases in the zone of the transmission surface to act on the subcaliber projectile. At the level of the driving plate, the tensile stress in the subcaliber projectile has the highest value; this stress changes over in the rearward direction toward the stabilizer into a compressive strain region; a compressive strain region likewise occurs once again toward the tip of the subcaliber projectile, due to the mass distribution in the forward zone of the subcaliber projectile.
In DE 2,836,963-A and EP 152,492-A, a sabot cage has been modified so that, in place of a driving plate, the driving surface has been spread apart in the axial direction, and the driving surface exhibits a sagging profile approaching the outer edge of the peripheral region of the projectile. The propellant charge cage encompasses approximately half the projectile. On account of the configuration of the driving surface, the shape-mating coupling between the projectile and the propulsion cage is improved, and the mass proportion of the propulsion cage is reduced. With such a configuration of the propulsion cage, the part of the projectile no longer surrounded by the driving surface can be torn off; the maximum propellant gas pressure is thereby limited.
The invention is based on the object of designing a maximally lightweight propulsion cage for a subcaliber projectile having such a structure that a maximally high propellant charge pressure can be utilized for the acceleration of the subcaliber projectile.
In order to attain this object, a propulsion cage is proposed in accordance with the invention which is characterized in that the driving surface extends from a forward guide zone to an end region of the subcaliber projectile.
It has been found surprisingly that a relatively lightweight propulsion cage of a synthetic resin can satisfy all requirements.
The introduction of force into the subcaliber projectile is distributed, by the propulsion cage according to this invention, practically uniformly over the entire jacket surface of the subcaliber projectile Thereby, the maximum values recede, and the stress curve in the propulsion direction becomes substantially more uniform. The occurrence of merely compressive strains, and of hardly any tensile stresses, can be achieved. With an identical transmission surface area, it is possible, for example, to more than double the force transmission from the propulsion cage to the subcaliber projectile with a conical contour of the propulsion cage as compared with a cylindrical contour.
In conventional propulsion cages similar to a dog's bone, the rearward, sealed driving plate also performs a guiding function within the barrel. In case of very long projectiles, equal-caliber stabilizers and/or radially projecting protuberances are required in most instances, according to EP 192,492-A. With the propulsion cage according to this invention, the plane of the centers of gravity of the driving surfaces already lies in the very close proximity to the center of gravity of the subcaliber projectile and the propulsion cage combined so that, if at all, little-stressed stabilizers are adequate, such as, for example, guide ribs at the rear end of the propulsion cage; in general, a sufficiently stable acceleration in the barrel is possible even without such additional guide elements. An improvement in the projectile stability is achieved.
In the propulsion cage according to the invention, the compressive strain occurring in the rearward zone of the subcaliber projectile is substantially identical to the static compressive strain which cannot be reduced any further on account of the gas pressure of the propellant charge. In contrast thereto, based on this structure, tensile stresses can be extensively avoided in the entire extension of the subcaliber ammunition, and the stress curve is generally low and smooth.
Although the propulsion cage of this invention permits very high propellant gas pressures, it is possible to manufacture this cage entirely of a synthetic resin, preferably from a carbon-fiber-reinforced synthetic resin; a preferred synthetic resin is epoxy resin. It has been found surprisingly that, on account of the rather uniform contact pressure over the entire surface of the subcaliber projectile, a flawless, high force transmission can be brought about from the propulsion cage to the projectile without the need for providing additional auxiliary means at the propulsion cage. Such conventional auxiliary means are, for example, a (separable) metallic sleeve within a propulsion cage of plastic, or mutually corresponding uneven areas between the projectile and propellant charge such as, for example, a thread cut into the projectile to provide longitudinally axially acting shapemating connection.
It may be advantageous, above all for reasons of manufacturing technique and/or engineering, to design a propulsion cage of a synthetic resin according to this invention so that it is not solid but rather has a ribbed, forwardly open structure. The thus-formed cavities must be filled out with corresponding cores of the same material or other materials on account of the required high compressive strength. Therefore, it is advantageous to fashion cavities in a wedge-like shape. Such cores are retained in their position due to mass moment of inertia during the acceleration phase of the subcaliber projectile. Such segments with thinner walls exhibit higher strength values, and possible problems in heat removal and shrinkage during manufacture can be more readily avoided. Another important advantage resides in that, by a special choice of material for the cores to be inserted, the properties of the propulsion cage as a whole can be still further improved. The properties of high-strength anisotropic materials can be optimally exploited for the skeleton of the segments of the propulsion cage as well as for the cores to be inserted.
It is especially advantageous to fill the cavities in the segments of the propulsion cage with wedge-shaped and platelike elements, the axis of the subcaliber projectile lying in the plane of the plate-like elements.
The plate-shape preferred for filling the cavities is to be imposed on the segmented propulsion cage also in still another form, namely by providing plate-like components between the individual segments of the propulsion cage, the mechanical property values of these components being optimized in the direction toward transmitting a maximally high propellant gas pressure to the subcaliber projectile. The increased manufacturing expenditure is not of very great significance inasmuch as the manufacture of anisotropic plate-shaped parts is relatively simple. Preferably, the plate-shaped parts are inserted in the cores and/or between the segments which are made of material with unidirectional fibers; whereas fiberfilled molded compositions are utilized for the wedge-shaped cores, or also for the segment skeleton.
Especially in case of plate-shaped elements for the cores, or plate-like components between the segments, it is possible to mold thereto, during manufacture, areas which act as flow-exposed surfaces in the propulsion cage and promote disintegration of the propulsion cage after exiting from the barrel.